To study the saponification value of an oil/fat by titrimetric method

Procedure

Follow these steps to determination of saponification value of Oil/Fat by titrimetric Method

  1. Preparation of sample:Weigh a known amount of oil/fat into a flask.
  2. Hydrolysis: Add a known volume of alcoholic KOH solution to the flask and heat the mixture under reflux for 30 minutes to ensure complete saponification.
  3. Titration:
    After hydrolysis, titrate the remaining (unreacted) KOH with a standard solution of HCl using phenolphthalein as an indicator. The appearance of a color change from pink to colorless marks the endpoint.
  4. Blank titration:
    A blank titration is performed using the same procedure without the oil/fat to account for the KOH that does not react with the fat.
  5. Calculation:
    The saponification value is calculated using the formula: Saponification Value=((B-S)*N*56.1)/W
    Where:
    B = Volume of HCl used for blank titration (mL)
    S = Volume of HCl used for sample titration (mL)
    N = Normality of HCl
    W = Weight of the oil/fat sample (g)
    56.1 = Molecular weight of KOH

Safety Precautions:

  1. Clamp the burette perfect vertically, so that it is easy to read the scale properly.
  2. Before use rinse the burette thoroughly, while filling the burette no air bubble should be present in the burette and dispense off working solution from the burette.
  3. Remove funnel after filling burette upto mark zero. Read the lower meniscus of the burette.
  4. KOH is highly caustic and can cause severe burns.
    Always wear appropriate personal protective equipment (PPE), including gloves and safety goggles.
    In case of skin contact, wash immediately with plenty of water.
    Ensure proper ventilation when working with alcoholic KOH to avoid inhalation of fumes.
  5. Ethanol (used in alcoholic KOH solution) is flammable. Keep it away from open flames, hot surfaces, or sources of ignition.
    Use in a well-ventilated area to avoid inhalation of vapors.
  6. To get better visibility of color change at the end point use filter paper below the conical flask.
  7. During titration conical flask should be stirred continuously and correctly observe the end point.